FOREST UTILIZATION 107 



The kiln is lighted at the narrow end and covered with green 



branches and earth in the usual manner. 

 The side walls being almost perpendicular, the cover is held in 



place by slabs spliced against the walls. No refilling is required. 

 Fire is conducted from the top of the kiln at the big end toward 



the bottom of the kiln at the little end. 

 The process lasts six to eight weeks. 

 The billets are placed horizontally, skidway fashion, the largest 



billets being put in the center and the smallest at the head and 



at the foot of the kiln. 



XXXIV. LAMPBLACK AND BREWER' S PITCH, AND THEIR MANUFACTURE. 



The former is used in the manufacture of patent leather; the latter for 

 pitching beer barrels. 



A. Raw material is spruce rosin. 



.. B. The process consists in a combined melting and pressing of rosin. 

 The brewer's pitch runs out through a pipe connecting the bases 

 of the melting vats with a cooling vat. 



C. The solid residue remaining in the vats is slowly burned in an 



oven. The smoke passes through a cool room and into a smoke 

 room, the top opening of which is covered by a common bag. 

 In this room pine soot or lampblack is deposited. The draft 

 is regulated by the attendant according to the shape or bulge 

 which the bag assumes under the influence of the smoke. 



D. Some turpentine can be derived at the same time if the vats are 



closed air tight and if the escaping gases are condensed in a 

 worm. 



XXXV. PYKOLIGNEOUS ACID, WOOD (METHYL) ALCOHOL, AND THEIR 



MANUFACTURE. 



A. Raw materials : These are, preferably, broad leafed species beech, 



birch, maple which must be thoroughly seasoned. 

 Heavy stuff is preferable, it is said, to small stuff. 



B. Distillation: The process consists in a dry distillation of the wood, 



differing from the charcoal kiln process merely by allowing the 

 gases to condense. 



The distillation takes place in large horizontal iron cylinders, 

 usually about 10 feet long by 5 feet in diameter, into which the 

 wood is run on steel trucks. After closing the cap of the cylin- 

 ders (admission of air reduces the output of pyroligneous acid) 

 the cylinders are slowly heated to a redhot. The gases forming 

 are led through long worm pipes into a condenser. 



Not all of the gases formed allow of condensation. The uncon- 

 densable gases are conducted to the fire room. 



At the bottom of the cylinder, tar is forming and is let out by a 

 system of pipes into a collecting basin. Conifers yield more 

 wood tar than hardwoods. 



